Security systems providing access to secured facilities based upon provision, by someone seeking access, of biometric information, require typically that a database of biometric signatures be searched for a match with a biometric signal (also referred to as a biometric input) provided by a user seeking access. Thus, for example, the user may present a fingerprint to a fingerprint scanning device, after which the security system will compare the received fingerprint with a database of fingerprint signatures in order to determine if the user is authorised to access to facility. Since biometric signatures are relatively complex, the search procedure can take a considerable time, particularly if the database of signatures is large. The time taken for this search can, if it becomes too large, cause inconvenience to users wishing to access the facility, and ultimately the use of such systems can fall into disfavour unless the search times are acceptably small.
Some present systems seek to reduce the search time by providing the user with a smartcard that contains the biometric signature of the user. In order to use this type of system the user firstly swipes the card at a card reader mounted adjacent to the secured facility, and then presses his or her finger against a fingerprint scanner. The system then matches the fingerprint signature generated by the fingerprint scanner against the fingerprint signature read from the card. This system does not maintain a database of fingerprint signatures, and operates on the basis that a user who presents such a card and who is able to provide a fingerprint signature that matches the signature of the card is entitled to access to the facility. Clearly this type of system suffers from the disadvantage that if a user becomes a security risk, for example, and the owners of the secure facility wish to exclude that user, then ancillary information is required in order to prevent such a user from accessing the facility, since the system as previously described will find a match between the information on the swiped card, and the fingerprint presented to the scanner.
Other current systems adopt a different approach which reduces the search space which is to be searched for a biometric signature match by asking the user to input an auxiliary PIN number. These systems require the user to firstly enter their PIN using a keypad, for example, after which the user presses their finger against a fingerprint scanner. The system uses the PIN to form a sub-address, thereby identifying a specific partition within the signature database, after which the system searches the aforementioned memory partition for a match with the fingerprint scanned by the fingerprint scanner. Although this system achieves a more rapid database search, this approach requires the user to remember a secret PIN and to enter it using keyboard. This type of system regards the PIN and the fingerprint input by the user at the fingerprint scanner to be two complimentary layers of security, thereby providing a higher level of security than a system based purely on the biometric signature comparison. However, this system is more cumbersome to use, and potential users can find the additional complexity undesirable.
Other systems use more powerful processors in order to search the signature database in less time. As the size of these databases increases, however, it becomes increasingly difficult and expensive to continuously upgrade the processing speed of the search computer.